Jacob silver sherman



(No Model.) Y

J. S. SHERMAN.

FOCAL CENTER OPTOMETER. No. 484,055. Patented '0611. 11, 1892*.

EUUNT THE [JETS :ns co., moro-urna, msumcwu u c UNITED STAT-Es l PATENTOFFICE.

JACOB SILVER SHERMAN, OF CASSOPOLIS, MICHIGAN.

FOCAL-CENTER OPTONIETER.

SPECIFICATION forming part of Letters Patent No. 484,055, dated October11, 1892. Application filed November 14, 1891. Serial No. 411,960. (Nomodel.)

To wZZ whom it may concern:

Be it known that I, JACOB SILVER SHER- MAN, a citizen of the UnitedStates, residing at Cassopolis, in the county of Cass and State ofMichigan, have invented a new and useful instrument,which I desire to beknown as the Focal-Center Optometer, of which the following is aSpecication.

My invention relates to improvements in optometers in which a movabletest design is used for the purpose of determining the power of lensnecessary to remedy certain defects in the vision of the eye.

Heretofore optometers have been used for the purpose of attaining thefocus of the eye without reference to the limits of said focus, whichwhile seemingly correct, in theory, the ordinary optometer is of limitedvalue in practice on account of the length of space over which the focusof the eye extends. The ilexibility of the lens of the eye and theeyeball together with the involuntary action of the orbital and ciliarymuscles on the eye, gives to it the power of adjusting the focus of itslens to any point within a certain limited space. The attaining of thelimits of said space and from them determining the focal center is thepoint which this instruoptical goods generally an instrument with whichthe center of the focus of the eye can be easily and accuratelydetermined.

In the accompanying drawings, Figure I, is shown an ordinary optometerprovided with lens-holder A', the test design E, Fig. 3, removed, andalso with a slot B in the arm A, which extends the full length thereof,the adj ustable measure C, Fig. 2, being made to t in the slot B, Fig-l,the adjustable collar D, Fig. 4, having the hole G, in which the pin H,Fig. 2, at the end of the measure C, Fig. 2, is adjusted, so that whenthe collar D, Fig. 4, is moved on the arm A, Fig. l, the measure C, Fig.2, moves with it, the collar D, Fig. 4, being placed on the arm A, Fig.I, next to the eye-piece and between the eye-piece and the test designE, Fig. 3, the adjustable collar F, Fig. 5, being placed on the arm A,Fig. l, between the test design E, Fig. 3, and the end of the arm A,Fig. 1, opposite the eye-piece,

I I I being set screws, the measure C, Fig. 2, passing freely throughthe test design E, Fig. 3, and the collar F, Fig. 5, in the slot B, Fig.I, when all are adj usted to their proper places, as shown in Fig. 6.

The instrument is operated inthe following manner: Placing the eye-pieceto the eye, holding the arm of the instrument horizontal1y, the testdesign E, Fig. 3, together with the collar D, Fig. 4, are moved towardthe eye until distinct vision ceases and a blur is obd served, at whichpoint the collar D, Fig. 4, is made fast by the set-screw I. Then thetest design E, Fig. 3, and the collar F,;Fig. 5, are together moved fromthe eye, passing the point of distinct vision, to the opposite end ofthe arm A, Fig. 1, until distinct visionagain ceases and the same degreeof 'blur is obtained, at which point the collar F is made fast by screwI. Then by determining the center between the collar D, Fig. 4, and thecollar F, Fig. 5, by means of test design E and the measure C, Fig. 2,the attaining of the focal center of the eye is accomplished.

It is evident that two arms and two lensbut desire that Letters Patentmay cover any device which comes clearly Within the spirit and scope ofmy discovery and invention.

Having thus described all that is necessary to a full understanding ofmy discovery and invention, what I claim as new isl. In an optometer,the combination of a lens-holder A', an arm A, an adjustable measure,collars D and F, and adjustable design E, as and for the purposes setforth.

2. In an optometer, a slotted arm A, prof vided with an adjustableLmeasure, in combination with a lens-holder, movable collars,

IOO

adjustable design E, and set-screws to retain the collars and design Ein fixed positions screws on said collars and design, substanafteradjustment, substantially as described tially as described and setfoi-th.

and set forth. JACOB SILVER SHERMAN.

3. The combination, in an ,optometeig of a Witnesses: 5 lens-holder A',arm A, test design adjustable JOHN L. YOsT, on arm A, an adjustablemeasure C, collar D, A. M. MOON, provided with an aperture G, collar F,and set- JOEL COWGILL.

